Not to drift off the subject too much, but I've heard that some hams many
years ago would drop there amp's HV transformers in a bucket of oil and run
the heck out of them, much over there rated current. Anyone out there ever
done that?
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Will Matney
Sent: Tuesday, March 21, 2006 5:08 PM
To: amps@contesting.com
Subject: Re: [Amps] RE : MW Oven Transformer question
Jos,
A man could put to in a container and pot them but heat don't escape that
easily this way I don't think. Some say potting makes them cooler by making
it like a heatsink. However, in calculating the heat loss in transformers,
insulation thickness has everything to do with it, including the outside
layer of paper. Then you have the hot spot for each winding which is at the
mean turn of each coil, and down in the center of the coil from top to
bottom. That heat has to escape and every bit of insulation causes this heat
to raise, not lower. Peter Dahl even uses a black die in his varnish which
is supposed to help dissapate the heat. Most people think it's something
other than varnish, or it's potted, but he did have it on his website at one
time what he done. Actually, I think you can buy that now pre-mixed. That's
the way I've been taught and is what's in every book on the subject. I'd
just as soon see a couple mounted on a common base, and connected together
like we're talking, out in mid air so they can breathe.
Best,
Will
*********** REPLY SEPARATOR ***********
On 3/21/06 at 10:54 PM hermans wrote:
>Hello Will,
>
>I have never seen a micro oven transformer from close, so I ignore its
>dimensions.
>Nice idea to construct some POTTED HV or HP transformers for the HAM
>world for cheap and make some money !
>A win win operation for both parties.......
>What say Will.
>
>73 Jos on4kj
>
>
>-----Message d'origine-----
>De : amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] De
>la part de Will Matney
>Envoyé : mardi 21 mars 2006 19:30
>À : amps@contesting.com
>Objet : Re: [Amps] MW Oven Transformer question
>
>
>Gerald,
>
>My guess by seriesing two will drop the flux density in each to around
>10 kilogauss as each will have 1/2 the line voltage across it. That's
>well below the bottom of the knee and in the linear region. It will
>raise the power capability X2 also, but I can't say how much without
>knowing the core dimensions. Two this way though will run as good or
>better than a lot of off the shelf linear transformers because of the
>low flux density. This means the efficiency is really high, probably 95%
>for a rough guess.
>
>Best,
>
>Will
>
>
>*********** REPLY SEPARATOR ***********
>
>On 3/21/06 at 2:22 PM TexasRF@aol.com wrote:
>
>>Thanks Will and John; I now have an understanding of the heating issues
>>with
>>the MOT. It appears that these transformers are really a poor choice
>for
>>continuous operation such as a filament power source. Two transformers
>>with the
>>primary and secondary windings series connected will work and for
>testing
>>the
>>traveling wave tubes is the quick method to be used.
>>
>>Many thanks for your help in my continuing education!
>>
>>73,
>>Gerald K5GW
>>
>>
>>
>>In a message dated 3/21/2006 11:10:15 A.M. Central Standard Time,
>>craxd1@verizon.net writes:
>>
>>If you want to add turns to the primary (if there's enough room, and
>>should be with the secondary removed), you can do a simple test to see
>
>>how many turns to add. First, use the formulas I published last week
>>about figuring the
>>core size and number of turns to find the correct number of turns for
>the
>>core
>>size you have. Next, connect the primary to 120 Vac and wind a 10 turn
>>coil
>>secondary. Take that secondary voltage and divide it by the 10 turns.
>>That
>>will be the turns per volt. Last, wind the extra turns you've found
>you
>>need by
>>the formulas and the known turns per volt. One good thing on this
>>transformer
>>in question, the primary is on the inside. If on the outside, you'd be
>
>>screwed on removing the secondary.
>>
>>Best,
>>
>>Will
>>
>>*********** REPLY SEPARATOR ***********
>>
>>On 3/21/06 at 11:42 AM John Popelish wrote:
>>
>>>TexasRF@aol.com wrote:
>>>
>>>> Not what I hoped to hear but I appreciate the good info!
>>>
>>>If you have a supply of this kind of landfill, you might put two
>>>similar units side by side, wire the primaries in series (effectively
>
>>>halving the volts per turn, so eliminating the saturation problems).
>>>Then you can knock the shunts out and wind a similar secondary on
>each
>>>(doubling the number of turns to compensate for the half primary
>>>voltage) and wire those two secondaries in parallel. This gives you
>a
>>>reasonably efficient transformer (that won't overheat without a fan)
>>>with about a kVA rating.
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>>
>>
>>
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>
>
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